Sign base



FIG. 1 is a perspective view of a sign base;

FIG. 2 is a top view of the sign base of FIG. 1;

FIG. 3 is a front view of the sign base of FIG. 1, which is the same as the rear view thereof; and,

FIG. 4 is a left side view of the sign base of FIG. 1, which is the same as the right side view thereof.

The bottom of the sign base of FIG. 1 is planar. However, no bottom view is shown or claimed herein, because the bottom of the sign base is not seen when the product is in use. 

CLAIM The ornamental design for a sign base, as shown and described. 